<!DOCTYPE html>
<html lang="">

<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Title Page</title>

    <style>
        .box {
            width: 0;
            height: 0;
            border: 10px solid;
            border-color: transparent transparent red red;
        }
    </style>
</head>


<body>
    <div class="box"></div>

</body>



</html>